1. Field of the Invention
The present invention relates to light sources and, more specifically, to fiber-based pulsed-light sources.
2. Description of the Related Art
Pulsed-light sources are widely used in optical communications systems and various scientific applications. For example, multi-wavelength synchronized pulsed-light sources are often employed in materials characterization experiments. A multi-wavelength synchronized pulsed-light source generates two or more pulse trains, each at a different characteristic wavelength. In this specification, the term xe2x80x9ccharacteristic wavelengthxe2x80x9d generally refers to a center wavelength (e.g., representing the highest power) in the spectral band corresponding to pulsed light. Different pulse trains generated by the synchronized pulsed-light source are synchronized with respect to each other, i.e., have fixed relative phases between the pulse trains and substantially identical pulse repetition rates. Characteristic wavelengths corresponding to different pulse trains can be changed (tuned) as necessary while the temporal synchronization is maintained.
A typical prior art multi-wavelength synchronized pulsed-light source is implemented using two or more optical parametric oscillators (OPOs), each pumped by the same laser source. An OPO is a device well known in the art that converts received light into light having a different characteristic wavelength. For example, a representative OPO may convert 20-nJ pulses at a fundamental wavelength of 0.8 xcexcm from a Ti:Sapphire laser into about 2-nJ pulses, whose characteristic wavelength may be continuously varied between about 1.1 and 1.6 xcexcm.
One problem with prior art multi-wavelength synchronized pulsed-light sources is that they are relatively expensive to implement primarily due to the cost associated with multiple OPOs. Another problem with said light sources is that the power conversion efficiency is relatively low, typically about 10%. Yet another problem with said light sources is their relatively large size, typically about 1xc3x972xc3x974 ft3, which hampers their use in portable or integrated devices.
The problems in the prior art are addressed, in accordance with the principles of the present invention, by an optical device including a microstructured fiber pumped by an external pulsed-light source. In one embodiment, the microstructured fiber includes two waist regions functioning as a tunable attenuator and a wavelength shifter, respectively. Output wavelength of the optical device is selected by attenuating the pump light in the first waist region and then passing the light through the second waist region to shift the pump energy to a new spectral band. An optical device of the invention configured with two or more microstructured fibers generates two or more synchronized pulsed beams, each at a different characteristic wavelength. Certain embodiments of the invention provide an inexpensive, compact, energy-efficient multi-wavelength synchronized pulsed-light source.
According to one embodiment, the present invention is a device, comprising: a beam splitter adapted to receive an input light beam having a characteristic input wavelength and to divide said input beam into N sub-beams, where Nxe2x89xa72; and N structured fibers, each adapted to receive and convert a different sub-beam into an output beam having a characteristic output wavelength different from the characteristic input wavelength, wherein at least two characteristic output wavelengths are different.
According to another embodiment, the present invention is a device, comprising a structured fiber including a first section and a second section optically coupled to the first section, wherein: the structured fiber is adapted to receive an input light beam having a characteristic input wavelength and to generate an output beam having a characteristic output wavelength different from the characteristic input wavelength; the first section is designed to operate as a wavelength shifter; and the second section is designed to operate as a first attenuator.